%0 Journal Article
%A Cisneros-Molina, José Luis
%T An invariant of $2\times 2$ matrices
%J The electronic journal of linear algebra
%D 2005
%P 146-152
%V 13
%I mathdoc
%U http://geodesic.mathdoc.fr/item/ELA_2005__13__a15/
%G en
%F ELA_2005__13__a15